1. Field of the Invention
This invention relates to a connector, more particularly to a connector which is suitable for high-speed transmission of electric signals.
2. Description of the Related Art
Conventionally, there has been proposed a receptacle connector comprised of three types of contacts, an insulator for holding the contacts, and a receptacle shell for covering the insulator (see Japanese Laid-Open Patent Publication (Kokai) No. 2002-334748).
The three types of contacts include a signal contact S and a ground contact G for high-speed transmission, and a contact D for non-high-speed transmission. Each of the three types of contacts has contact portions which are capable of being brought into contact with contact portions of mating contacts of a mating connector, and terminal portions which are capable of being soldered to pads on a printed board.
The contact portions are arranged in two rows, one above the other (see FIG. 7(b) in the above-mentioned Patent Publication) One ground contact G in the upper row and a pair of signal contacts S and S in the lower row which are located below the ground contact G form one contact group for high-speed transmission, while one ground contact G in the lower row and a pair of signal contacts S and S in the upper row which are located above the ground contact G form one contact group for high-speed transmission.
The terminal portions are arranged in a row along the direction of the width of the insulator (the contact arranging direction). One ground contact G and a pair of signal contacts S and S located on opposite sides of the ground contact G form one contact group for high-speed transmission.
In the above-described arrangement of the contact portions, only the pair of signal contacts S located at a right end in the upper row are not in a state sandwiched by ground contacts G. As a result, variation in transmission characteristics is caused between the pair of signal contacts S and the other pairs of signal contacts, and there is a fear that crosstalk may occur between the pair of signal contacts S and other pairs of signal contacts located obliquely below.
Further, in the arrangement of the terminal portions, the signal contacts of adjacent contact groups in the direction of the width of the insulator are adjacent to each other, and hence there is a fear that crosstalk occurs between these signal contacts.
Furthermore, since the terminal portions are arranged in a row along the direction of the width of the insulator, the connector suffers from the problem of an increase in size.
The present inventors invented a connector for solving the problems, and the present assignee filed a patent application for the invention (Japanese Patent Application No. 2008-39099).
In this connector, the contact portions of the signal contacts for high-speed transmission and the contact portions of the ground contacts for high-speed transmission are arranged in a row in a contact arranging direction which is orthogonal to a connector fitting direction. Each pair of the contact portions of the signal contacts for high-speed transmission are disposed between the contact portions of ones of the ground contacts for high-speed transmission which are adjacent in the contact arranging direction.
Further, the contact portions of the contacts for non-high-speed transmission are arranged in a row in the contact arranging direction. The row formed by the contact portions of the signal contacts for high-speed transmission and the contact portions of the ground contacts for high-speed transmission, and the row formed by the contact portions of the contacts for non-high-speed transmission are parallel to each other.
Therefore, variation in transmission characteristics and crosstalk are suppressed.
Further, the connection portions of the signal contacts for high-speed transmission and the connection portions of the ground contacts for high-speed transmission are arranged in a row in the contact arranging direction. The connection portions of each pair of the signal contacts for high-speed transmission are disposed between the connection portions of ones of the ground contacts for high-speed transmission which are adjacent in the contact arranging direction.
The connection portions of the contacts for non-high-speed transmission are arranged in the contact arranging direction. The row formed by the connection portions of the signal contacts for high-speed transmission and the connection portions of the ground contacts for high-speed transmission, and the row formed by the connection portions of the contacts for non-high-speed transmission are parallel to each other.
Therefore, variation in transmission characteristics is suppressed, and it is possible to reduce the size of the connector.
However, although the connection portions of the contacts for non-high-speed transmission each have a surface-mount type planar shape and are reflow-soldered to pads of a printed board, these connection portions are between the contact portions and connection portions of the signal contacts for high-speed transmission and the ground contacts for high-speed transmission in the fitting direction and below the housing. This prevents the soldered state of the connection portions from being checked (viewed).
Further, when the connector is removed from the circuit board so as to repair the same, although the connection portions of the signal contacts for high-speed transmission and the ground contacts for high-speed transmission protrude out of the housing, and hence it is possible to directly apply a soldering iron to the connection portions, but the connection portions of the contacts for non-high speed transmission are positioned below the housing, and hence it is difficult to directly apply the soldering iron to the connection portions. Therefore, it is difficult to remove the connection portions for non-high-speed transmission from pads of the printed board.
Although a method can be envisaged in which the printed board having the connector mounted thereon is placed in a reflow oven to thereby melt the solder instead of directly applying the soldering iron to the connection portions, the method is not appropriate for melting the solder since soldered portions of electronic parts mounted on the printed board other than the connector are also melted, which can cause undesired effects, such as making the electronic parts movable.
Therefore, it is practically impossible to remove the connector from the printed board after all, and hence there is no other way than to repair the connector in a state mounted on the printed board.
Thus, the present inventor became aware that the connector filed as the invention with the Japanese Patent Office for a patent application by the present assignee suffers from a problem that it is impossible to check the soldered states of the connection portions of the contacts for non-high-speed transmission or it is difficult to remove the connector from the printed board.